192 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
had an opportunity to search for it. The further part of Cape Cod, 
beyond Dennis, offers at the present day but little ground suitable 
for Evotomys; and though it may possibly be found in small 
numbers, here and there, as far down the Cape as Orleans, I do not 
think it exists beyond that town. The most favorable locality I 
know of in any of the townships north of Orleans, is a thick cedar 
swamp at South Wellfleet, and here Mr. Brown spent a week trap¬ 
ping for it for me, but he obtained none. This is not surprising, for 
between this point and Orleans the township of Eastham interposes 
a barren waste of dry gravel, reaching from one side of the Cape to 
the other, and extending along it for miles,— a barrier that well 
might prove impassable to such an animal as Evotomys. Probably 
it is safe to say that, with these exceptions, it is to be found through¬ 
out eastern Massachusetts wherever favorable conditions exist. 
What these favorable conditions are, is the most interesting ques¬ 
tion connected with the animal’s distribution, but it is not one that 
can receive a positive and final answer. Nevertheless there are 
some characteristic features that are common to almost all of the 
places where I have found it. One may look for it with some con¬ 
fidence in almost any large tract of wet ground that retains its 
moisture through the summer, but is not subject to serious floods, 
and which bears a growth of woods sufficiently heavy to afford a 
dense shade, so that the ground beneath, and the roots of the trees, 
are covered with a deep carpet of sphagnum. If the older trees 
have been suffered to die a natural death, and their stumps and 
fallen trunks lie slowly rotting on the ground, half-concealed by the 
sphagnum, the chance of finding it is certainly not lessened. One of 
the most evident peculiarities of such a spot as this, in southern New 
England, is that the dense shade and the abundant evaporation 
maintain a temperature during the hottest summer weather that is 
far below that of the surrounding country. In these respects of 
coolness, moisture, and shade, there is a striking resemblance to the 
woods Evotomys gapperi inhabits in extreme northern New Eng¬ 
land and other parts of the Canadian zone. 
The places where I have found it differ considerably in their 
appearance, chiefly according to the kinds of trees with which they 
are wooded. In the southern counties the conditions I have named 
are best afforded by the “ cedar swamps ” that once were such a 
characteristic feature of that part of the State. These are tracts of 
low ground, varying in area from a few acres to sometimes several 
